


Sinful desires

by Anonymous



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Modern Setting, F/M, Sibling Incest, Step-Sibling Incest, doro teaches edie some stuff, dorothea makes a cameo
Language: English
Status: Completed
Published: 2020-10-30
Updated: 2020-10-30
Packaged: 2021-03-08 23:26:59
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,237
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27284896
Author URL: https://archiveofourown.org/
Summary: Now, El has a habit of sneaking into Dimitri’s room whenever she couldn’t sleep or had a nightmare. He didn’t mind of course, he never did, he is more than happy to help soothe her and drive the nightmares away. But, even he has his limits.
Relationships: Dimitri Alexandre Blaiddyd & Edelgard von Hresvelg, Dimitri Alexandre Blaiddyd/Edelgard von Hresvelg
Kudos: 39
Collections: Anonymous





	Sinful desires

As the sun started to rise to bring upon a new dawn, so does Dimitri and the rest of his family. The Blaiddyd household was silent apart from the soft whimpers his step-sister let out in her sleep. 

  
  


It has always been like this since his father married Edelgard’s mother 10 years ago. At first, Edelgard— El, may seem like a sweet ordinary little girl that everyone tends to see her as, but they didn’t know that the girl who taught him how to dance, how to play the piano, and the little one who likes sweets and to paint was the same Edelgard that had terrible nightmares and cries when no one is looking. 

  
  


Dimitri first found out the cheery little girl’s secrets when he was sent by his step-mother to fetch her for dinner. He heard sobs and whimpers behind the tall door of Edelgard’s room. Although muffled; he knew that his sister was crying. 10 year old Dimitri rushed to little Edelgard’s room and hugged her until she calmed down. 

His mother— probably worried that something had happened to her children, climbed up the stairs and frowned as she saw the door open. Her brows uncurled to a fond expression when she saw the scene in front of her. Neither children noticed that their mother looking over them with a certain fondness in her motherly features. Their mother smiled when Dimitri eventually walked towards the dining room with little Edelgard trailing behind him, one hand holding his, and the other she held a stuffed bear in her arm. 

  
  


Lambert smiled at his children, he raised a brow as he saw the stuffed bear in Edelgard’s arm. As if she was questioned, Edelgard said, “Dima gave this to me, papa! Isn’t he cute?” 

  
  


“I hope you don’t mind dad. El needs him more than i do.” Both parents turned to look at each other, smiling fondly towards Dimitri before finally turning their eyes towards Edelgard. Patricia went ahead and hugged their children before preparing them their dinner as a family. 

  
  


  
  


———•••———

  
  


  
  


Now, El has a habit of sneaking into Dimitri’s room whenever she couldn’t sleep or had a nightmare. He didn’t mind of course, he never did, he is more than happy to help soothe her and drive the nightmares away. But, even he has his limits. 

  
  


How could he not? She was not the 9 year old girl anymore. She was a grown woman now. A blossoming young lady in the Blaiddyd manor. And throughout the years, her lithe tiny frame was replaced by a more accentuated, he was not one to drool around while looking at women. But, _ugh_. _Goddess_ forgive him— he had sinned immensenly, for he had not once, not twice, but a couple of times had spared a glance at his step-sister’s beauty. How could he not? When he and Edelgard was still in school, all of the boys and girls had been smitten with his step-sister. It made his blood boil, and heart twinge in jealousy. 

  
  


Edelgard didn’t notice however, as she only focused on her dream of working at their father’s company, and Edelgard, ever the studious student, wanted nothing more than to surpass all her other classmates to prove to Lambert and her mother that she is capable of earning herself a seat in Lambert’s board meetings. He too, one day wanted to help his father with his job. 

  
  


Dimitri winced as he looked down at her shapely bottom shifting against his stiffness. This was wrong. Terribly, horribly, incredibly wrong. 

  
  


But, El didn’t seem to care as she opened her eyes and stretched her arms and legs, brushing her thighs against his hard tent unconsciously. Edelgard said nothing at first, but then she turned around and looked up at her step-brother with those sleepy eyes. “Morning, dima. Did you sleep well?” 

  
  


Dimitri tried his best to remain calm as he gazed at her, “Good morning, El. Yes, i did. You were having a nightmare again though,” Edelgard widened her eyes slowly, gulping as she looked away, guilt in her eyes, “Sorry, did i wake you?” 

  
  


Dimitri whispered a “No.” before leaning down to kiss her forehead. It was a brotherly thing to do— at least that’s what he thought. El didn’t seem to mind it. His parents didn’t mind it too. So, he does it out of habit and reflex. 

  
  


“Alright, if you say so...” Edelgard trailed as she looked downwards at his growing tent. The corner of her lip raising up to form an amused smirk, she tries very hard to not dive in just yet. She needs to make it up to his step-brother after all. 

Dimitri didn’t seem to notice that El knew about his boner. _Oh,_ Edelgard was going to have so much fun teasing her step-brother.

  
  


“Dima?” Edelgard called, maintaining her calm demeanor. She might have passed as an innocent lady, were it not for her growing urge to take her brother right there and now. 

  
  


“Yeah, El? Do you need something?” 

El smiled at the nickname, she _loves_ it when her friends and family called her that, especially if it’s Dimitri. 

  
  


Edelgard’s smile turned sly as she grazed his tent with her thigh. Earning a sharp hitch of breath from Dimitri. A groan, escaped his mouth as she followed it up with a whisper on his ear, “I don’t think i’m the one who needs _‘something’_ ” Edelgard nibbled at his ear, before backing away, giving him a smirk. 

  
  


“El...please don’t do this.” Dimitri pleaded as Edelgard started to get closer to him, her generous chest brushing against his cotton shirt. He could feel her nipples hardening as she pressed herself towards him. It aroused him even more. "We can't.." But, El ignored him.

  
  


It took a while before realizing that her step-sister had only wore a small body-fit tank top, with thin straps and very tiny shorts to bed. It didn’t seem like she was wearing any underclothes beneath them, her hardened nipples against him were proof enough. 

  
  


Still, he has to stop her before it escalated into something the both of them might come to regret. 

  
  


“Stop? Are you sure, _Dima?_ ” She whispered, holding a finger to his chest, dragging it slowly down his figure, and stopping until it arrived at the front of his sleeping shorts. “You’re already _this_ hard. I wouldn’t want my dear brother of mine to suffer all day without _any_ relief...” she continued, teasing him by circling his tent with a manicured finger. 

  
  


This was torture. Dimitri Alexandre Blaiddyd was going to rot in hell for doing what he is going to do after this. If that is his fate, then so be it. He was too smitten and in love with his so called little step-sister to care about the after life. 

  
  


So, Dimitri groaned and said _“Fuck it_. _”_

  
  


Edelgard was caught off guard as Dimitri surged in to grab her cheeks gently and crushed his lips against her plump ones. Edelgard hummed as she kissed him back, not wanting to lose to him, she let out her tongue and Dimitri let her in, kissing her roughly, he grabbed her waist tightly, earning a small moan from his sister. 

  
  


_Oh, how sinful._ He should not be doing this to his own sister. His step-sister. 

“El... _please._ ” Dimitri muttered between their kisses. Edelgard hummed as she sat up begrudgingly, giving him a chaste kiss before going down and propping herself between his long legs. 

  
  


Edelgard tugged at his shorts, she toyed with the edge of his boxers, eyeing him from below, Dimitri nodded once, giving her silent permission. 

  
  


She dragged the shorts and boxers down his legs, not even bothering to throw them away. As the cold air reached his hard cock, Dimitri shivered as El licked her lips at the erotic sight of her brother’s rod. It was quite _big_ — bigger than what she was used to seeing at the erotic books she tends to read. She had never done this before, nor has she ever tried to, but she knew the basics of having sex or in this case, giving your step-brother a blowjob.

  
  


Dorothea, one of her best friends, told a story about how she once gave a _‘head’_ to her first boyfriend at his parent’s house. When Edelgard heard that, her face grew red of embarrassment, what’s more is that her friend had the audacity to give her a lewd demonstration in front of her ans some other friends— granted they were all quite drunk, but she still remembered it like it was yesterday. 

  
  


Now, to put that demonstration to good use...

  
  


Edelgard dragged a finger from the throbbing head down to his balls, repeating the action over and over again, until Dimitri couldn’t hold it any longer. 

  
  


“El, please stop teasing...” El smirked, as she puffed a hot breath towards the head, groaning, Dimitri held her head, and led it closer to his stiffness. As if smelling his lust, she licked the head first, tasting the pre-cum inside her mouth. Humming pleasantly, she says, “ _My, my,_ brother. How needy and lewd you are...is this how you feel towards me? Do you want to me to take you inside my mouth?” Edelgard fluttered her eyelashes seductively, as Dorothea had taught her how to when she needed someone to do her a favor. 

  
  


Dimitri hitched a breath, before letting out a shaky, “ _Yes._ Goddess, El, you look so beautiful, _I-_ please, take me,” That was all she needed to hear. 

  
  


Edelgard licked the sides of his cock, while holding it with one hand. Then, she proceeded to part her lips, grazing the top of his head and finally taking him inside her mouth slowly. Dimitri let out a moan, chuckling Edelgard started to pump his hard cock with her lithe fingers, simultaneously bopping her head up and down. 

  
  


_“Goddess, Ah—! Your mouth!”_

  
  


She continued doing so, until she found a rhythm, her eyes never leaving his heavy-clouded gaze, it was intoxicating. As she felt her own wetness spreading onto her shorts. But, she instead focused on Dimitri’s pleasure first. After all, this was her fault in the first place. 

  
  


_“Fuck, El, Ah— shit!”_ El had teased his balls with her free hand, it made him even more sensitive. He held onto Edelgard’s head, yanking her brown hair gently. Edelgard seemed to like the idea, as seen by her increasing pace of pumping his cock. 

  
  


Dimitri held a breath before raising his hips, thrusting into her mouth a couple times to meet her pace. 

  
  


_“Yes, Ah— damn! Just like that, El!”_ He chanted Edelgard’s name as she sucked on his raw cock over and over again. Dimitri let out a quiet groan as he finally released inside her mouth. 

  
  


His half-lidded gaze turned dark as he eyed the way his little sister drank it all up, even going out of her way to clean the stains he left on his stomach and thighs. Once she finished, she let out a thumb with a pop, and smiled innocently at him. 

  
  


What a truly sinful act indeed. 

  
  


Although his cock was saying otherwise. As it still stood tall, even though it went through a whole lot of torture from Edelgard. 

  
  


Damn him. For letting his sister get away with this. 

  
  


Dimitri leaned forward to sit up, and gently grabbed Edelgard’s waist as he kissed her cheek, “Thank you, El. Your help was, _ah_ , deeply appreciated.” 

  
  


Edelgard giggled, “It’s the least i could do, Dima. _Although..._ ” she trailed, shifting her weight to place herself onto his lap, grinding herself against his cock gently. 

“I don’t think you’re nearly done yet, are you?” Dimitri huffed, kissing her to shut her up. Breaking the kiss, he nudged at the tank-top she was wearing. With some help from Dimitri, Edelgard was now fully nude on his bed. Locking her legs at each side of his waist she rubbed her clit slowly against him, finding a good enough friction as he watched her please herself. 

  
  


Edelgard is beautiful. Even more so like this, without anything hiding her fair skin. While El is busy trying to please herself, Dimitri tried to distract himself by feeling her perky breast, teasing her nipples, and kissing her neck and collarbone. 

  
  


_“Oh, Dima—!”_ Edelgard moaned. 

  
  


“What do you want, El?” Dimitri asked softly, biting her nipples and giving each of her mounds a kiss as he waited for her answer. 

  
  


“Ah— I-i want you, Dima, _please,_ ” she pouted, “Want me to what? Be more specific, El, didn’t mom taught us that?” 

  
  


Edelgard let out a needy moan, biting her lips, “I want you inside me. I want you to make love to me, Dima.” She breathed, staring up at Dimitri. 

  
  


Dimitri grinned as she smacked El’s bottom. “Good, now how do you want me? On top? From behind? What, El? Tell me.” 

  
  


Edelgard whimpered, as she let out a small laugh, “I always dreamed about...you fucking me from behind, our front to-towards the door...and i dreamt that— mama and papa would scold us half to death when they found out we’re having sex.” Dimitri groaned as she said that, “You— you really dreamt of that scenario?” 

  
  


Edelgard nodded, “It was scary, i think we should keep it down...or else mama and papa will know..” Dimitri licked his lips, pressing a kiss on her lips, “Alright. But, i don’t plan on slowing down...” 

  
  


Edelgard blushed at the Dimitri’s statement. Dimitri held her waist, as she sticked out her bottom more, spreading her legs, to enable him to enter her easily. 

  
  


“Are you on..?” 

  
  


Edelgard chuckled, “Birth control? Yes, now please, Dima, i _need_ you..” she begged, it almost sounded like a whine. 

  
  


Well, who was he to deny his lover’s wish? 

  
  


Dimitri entered her slowly, both of them gasped at the newfound friction, it took a while before Edelgard got used to the pain, Dimitri helping her through it by pressing soft kisses on her shoulder blades and whispering sweet things like he usually does when she had a nightmare. 

  
  


“Dima— _ah—_ move please..” At her command, he moved slowly at first, tuning out the noises of the tv inside his room, focusing instead at the moans and whimpers her step-sister let out. 

  
  


It was Edelgard’s idea to turn on the tv, since his and Edelgard’s room was upstairs, doesn’t mean that their soundproof. It’s better to be safe than not at all. 

  
  


Picking up the pace, he kept thrusting back and forth, earning muffled moans from his lover. His own moans overlapped with the slapping sounds of their skin against each other. He gritted his teeth as Edelgard let out a particularly high-pitched moan, _“Ahhh—! Right there, Dima! Oh, shit, harder!!”_

  
  


Edelgard was not one to plead or beg. It seemed to him, that she and him both had wanted this to happen for goddess knows how long. 

  
  


He complied, he granted her wish. He backed away until only his head poked her entrance, Edelgard whined as the warmth inside her left momentarily. Dimitri took a deep breath before he thrusted as hard as he could, a loud muffled moan escaped El’s lips. He hissed when he felt her getting tighter around him, he could tell by her frantic movements and moans that she was close. And so was he. 

  
  


Dimitri used his last remaining energy by thrusting faster and deeper inside her step-sister’s warm hole. The slapping sounds grew ever louder, just as Edelgard was reaching her peak, there was a knock. 

  
  


Both of them widened their eyes as they realized who it was. The door was thankfully locked, but, still, if their parents heard their lustful moans and saw the position they’re in right now, they would be very sure that they were going to get disowned or something worse. 

  
  


“Dimitri? Are you in there?” It was Lambert, their father. Dimitri gritted his teeth, resisting the urge to continue to move inside his sister’s lower lips. And El definitely wasn’t helping one bit, she wiggled her hips backwards to gain more pleasure when he stopped moving. Dimitri thinks that she was doing this on purpose, as seem from the small smirk on her face, despite her saying that she doesn’t want to risk having caught by someone at all. 

  
  


Dimitri cleared his throat, “..yes, dad. What is it? Do you need anything?” 

  
  


Edelgard let out a whimper. He froze, hoping the sound of the movie playing in the background covered the sound El let out.

  
  


“Ah, is El with you? I thought i heard her.” 

  
  


He stiffened, but he decided to play it cool, “Yeah, El’s here. We’re watching a movie—“

  
  


Edelgard moved against his cock faster. 

  
  


“—A horror movie. El’s a little bit scared right now.”

  
  


He could hear his father’s amused chuckle from outside of his door. “I’m glad both of you are having a great time together! I just came by to tell you two that me and your mom are going out for dinner, you guys wanna come with? Or do you just want some takeaways?” 

  
  


“Takeaways, please!” Edelgard managed to let out her usual calm tone. 

“Alrighty! Dimitri, my boy! Take care of your little sister while we're gone, alright?” 

  
  


“Yes dad!” 

  
  


As the footsteps grew faint, and when they made sure that their parents were out of the manor, Dimitri wasted no time than to continue to fuck Edelgard as rough as he could. Edelgard hummed pleasantly, huffing, "Finally. I thought he wasn't going to leave-- Ah--"

“You were teasing me weren’t you, El? Did you want dad to find out about this?” 

" _Mmm!_ no, it's just-- it feels _so good_ inside, that _I-- ah,_ I simply couldn't resist.." 

Edelgard, no longer having to muffled her moans, whined loudly, panting as Dimitri grabbed her chin to face him, kissing her now swollen lips, he kept his brutal pace, not planning to stop until both are equally wasted. 

_“Ahhhh—! Dima, yes, yes! so c-close!”_

  
  


Dimitri kept his eyes on her lavender ones, leaning down to whisper, “Let go for me, El. _Cum for me._ ” 

  
  


A high-pitched moan could be heard around the room, his own groans filling the warm air around them. Dimitri rocked back and forth, easing Edelgard’s orgasm whilst doing so. 

  
  


As he pulled out, he could see his seed dripping down Edelgard’s thighs. 

  
  


It was then that Dimitri had got pulled out from his sinful activity with his step-sister. 

  
  


Perhaps, Dimitri is going to hell for this. 

  
  


  
  


———•••———

  
  


  
  


Dimitri gazed at Edelgard’s sleeping form. She was snuggled up against his naked chest, it seemed that the activity had tired her out to the point where she collapsed when they finished. 

  
  


Thankfully, he was able to clean his sheets and her dirty clothes before joining her in his bed. It was warm. He was content like this. As silence took over the room, he began to ponder what this means for the both of them. What he felt towards her was not of plain lust, no, it was something more. 

  
  


Edelgard rubbed her eyes, and smiled up at him, kissing the corner of his lips, “Did you sleep well, Dima?” 

  
  


Dimitri smiled softly at Edelgard, pulling her closer to him, he reciprocated the kiss. 

"I will, now that you're here."

  
  


Yes. Perhaps, he had indeed fallen for Edelgard. He supposed that he could sleep well, now that he has her in his arms.

  
  


  
  



End file.
